U.S. patent application number 11/790147 was filed with the patent office on 2007-11-08 for hard disk drive, method for controlling fod voltage thereof, and computer readable recording medium recording the method.
Invention is credited to Jin-Wan Jun.
Application Number | 20070258164 11/790147 |
Document ID | / |
Family ID | 38660945 |
Filed Date | 2007-11-08 |
United States Patent
Application |
20070258164 |
Kind Code |
A1 |
Jun; Jin-Wan |
November 8, 2007 |
Hard disk drive, method for controlling FOD voltage thereof, and
computer readable recording medium recording the method
Abstract
A flying on demand (FOD) voltage of a hard disk drive (HDD) is
controlled by detecting a shock occurring to the HDD on which a
magnetic head that records data on a disk or reproduces data from
the disk is mounted, and if the shock is detected, controlling the
FOD voltage that is applied to the magnetic head to thermally
expand an end of the magnetic head.
Inventors: |
Jun; Jin-Wan; (US) |
Correspondence
Address: |
VOLENTINE & WHITT PLLC
ONE FREEDOM SQUARE, 11951 FREEDOM DRIVE SUITE 1260
RESTON
VA
20190
US
|
Family ID: |
38660945 |
Appl. No.: |
11/790147 |
Filed: |
April 24, 2007 |
Current U.S.
Class: |
360/75 ; 360/60;
G9B/5.198; G9B/5.23 |
Current CPC
Class: |
G11B 5/6005 20130101;
G11B 2005/0005 20130101; G11B 5/02 20130101; G11B 5/5582 20130101;
G11B 5/6064 20130101 |
Class at
Publication: |
360/75 ;
360/60 |
International
Class: |
G11B 21/02 20060101
G11B021/02; G11B 15/04 20060101 G11B015/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2006 |
KR |
10-2006-0039446 |
Claims
1. A method for controlling a Flying On Demand (FOD) voltage within
a hard disk drive (HDD) comprising a disk and a magnetic head that
records data on or reproduces data from the disk, the method
comprising: detecting a shock applied to the HDD; and upon
detecting the shock, controlling the FOD voltage applied to the
magnetic head to thermally expand one end of the magnetic head.
2. The method of claim 1, wherein the controlling of the FOD
voltage comprises: removing the FOD voltage from the magnetic head
to increase the flying height of the magnetic head with respect to
the disk.
3. The method of claim 1, wherein the controlling of the FOD
voltage comprises: storing a value of the FOD voltage applied to
the magnetic head; and after the shock ends, reapplying the FOD
voltage corresponding to the stored value of the FOD voltage.
4. The method of claim 3, wherein the controlling of the FOD
voltage comprises: distinguishing whether the FOD voltage is
applied to the magnetic head; and if the FOD voltage is not applied
to the magnetic head, waiting until the shock ends while
maintaining the state of the FOD voltage; and if the FOD voltage is
applied to the magnetic head, controlling the FOD voltage applied
to the magnetic head and waiting until the shock ends.
5. The method of claim 4, wherein controlling the FOD voltage
applied to the magnetic head comprises removing the FOD voltage
applied to the magnetic head.
6. The method of claim 4, further comprising: stopping operation of
the magnetic head when the shock is detected; and after the shock
ends, retrying operation of the magnetic head before reapplying the
FOD voltage corresponding to the stored value of the FOD
voltage.
7. The method of claim 6, wherein operation of the magnetic head is
a data reproduction operation.
8. The method of claim 6, wherein operation of the magnetic head is
a data recording operation.
9. A computer readable recording medium recording a method for
controlling a Flying On Demand (FOD) voltage within a hard disk
drive (HDD), the HDD comprising a disk and a magnetic head that
records data on or reproduces data from the disk, and the method
comprises; detecting a shock applied to the HDD, and upon detecting
the shock, controlling the FOD voltage applied to the magnetic head
to thermally expand one end of the magnetic head.
10. A hard disk drive (HDD) comprising: at least one disk; a
magnetic head recording data on the disk or reproducing data from
the disk and having one end that thermally expands in relation to
an applied Flying On Demand (FOD) voltage; a shock sensor detecting
an external shock applied to the HDD; and a controller controlling
the FOD voltage in response to a detected shock.
11. The hard disk drive of claim 10, wherein upon shock detection,
the controller removes the FOD voltage applied to the magnetic head
to increase the flying height of the magnetic head with respect to
the disk.
12. The hard disk drive of claim 10, wherein upon shock detection,
the controller stores a value of the FOD voltage applied to the
magnetic head, controls the FOD voltage applied to the magnetic
head, and reapplies the FOD voltage corresponding to the stored
value of the FOD voltage to the magnetic head after the shock
ends.
13. The hard disk drive of claim 12, wherein the controller
distinguishes whether the FOD voltage is applied to the magnetic
head; and if the FOD voltage is not applied to the magnetic head,
the controller waits for the shock to end while maintaining the
state of the FOD voltage and if the FOD voltage is applied to the
magnetic head, the controller controls the FOD voltage applied to
the magnetic head and waits for the shock to end.
14. The hard disk drive of claim 13, wherein the controller
controls the FOD voltage applied to the magnetic head by removing
the FOD voltage.
15. The hard disk drive of claim 14, wherein upon shock detection,
the controller stops the operation of the magnetic head, stores a
value of the FOD voltage applied to the magnetic head, retries the
operation of the magnetic head after the shock ends, and reapplies
the FOD voltage corresponding to the stored value of the FOD
voltage to the magnetic head.
16. The hard disk drive of claim 15, wherein the operation of the
magnetic head is a data reproduction operation.
17. The hard disk drive of claim 15, wherein the operation of the
magnetic head is a data recording operation.
18. The hard disk drive of claim 10, wherein the shock sensor is
mounted on a printed circuit board including the controller.
19. A hard disk drive (HDD), comprising: at least one disk; a
magnetic head recording data on the disk or reproducing data from
the disk and having one end that thermally expands as an Flying On
Demand (FOD) voltage is applied; a shock sensor detecting an
external shock applied to the HDD; a controller generating a signal
for removing the FOD voltage when the shock sensor detects the
shock; and a pre-amplifier receiving the signal for removing the
FOD voltage from the controller and removing the FOD voltage
applied to the magnetic head.
20. The hard disk drive of claim 19, wherein, when the shock sensor
detects the shock, the controller generates a stop signal stopping
operation of the magnetic head and the signal for removing the FOD
voltage in synchronous with the stop signal.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a hard disk drive (HDD), a
method for controlling a Flying On Demand (FOD) voltage within the
HDD, and a computer readable recording medium recording the method.
More particularly, the invention relates to a HDD, a FOD voltage
control method, and related computer readable recording medium in
which the HDD includes a magnetic head having improved recording
and reproduction capabilities which simultaneously prevent damage
to the magnetic head and/or a disk within the HDD when a shock is
applied to the HDD.
[0003] This application claims the priority of Korean Patent
Application No. 10-2006-0039446, filed on 2 May 2006, the subject
matter of which is hereby incorporated by reference.
[0004] 2. Description of Related Art
[0005] Hard disk drives (HDDs) include a collection of electronic
and mechanical parts. HDDs function as memory devices adapted to
record and reproduce data by converting digital electrical pulses
to/from corresponding magnetic field impulses. HDDs provide
permanent data storage on one or more disks containing a plurality
of defined data "tracks". HDDs are widely used as auxiliary memory
devices in computer systems because of their ability to rapidly
access large amounts of stored data.
[0006] With recent increases in track per inch (TPI) data storage
density, as defined by a direction around the rotational axis of a
disk, and bits per inch (BPI) data storage density, as defined by a
direction across the thickness of a disk, contemporary HDDs are
able to achieve very high capacity data storage with relatively
small size. However, as the data storage capacity has increased
while the size of contemporary and emerging HDD has actually
decreased, the flying height (FH) for a constituent magnetic
head--that is, the height at which the magnetic head floats above
the disk surface--must be reduced to maintain or improve the
recording and reproduction capability of the HDD.
[0007] Unfortunately, as the FH for a magnetic head decreases, the
likelihood of impact or collision between the magnetic head and the
disk surface increases. This is particularly true when the HDD is
subjected to an externally applied impact or shock. Under such
circumstances, the risk of damage to the magnetic head and/or disk
is very great.
SUMMARY OF THE INVENTION
[0008] Embodiments of the invention provide a hard disk drive (HDD)
having improved recording and reproduction capabilities associated
with a magnetic head and yet simultaneously inhibit damage to the
magnetic head and/or a disk surface in relation to an externally
applied shock. Embodiments of the invention also provide a related
a method for controlling an FOD voltage within the HDD and a
computer readable recording medium recording the method.
[0009] In one embodiment, the invention provides a method for
controlling a Flying On Demand (FOD) voltage within a hard disk
drive (HDD) comprising a disk and a magnetic head that records data
on or reproduces data from the disk, the method comprising;
detecting a shock applied to the HDD, and upon detecting the shock,
controlling the FOD voltage applied to the magnetic head to
thermally expand one end of the magnetic head.
[0010] In another embodiment, the invention provides a computer
readable recording medium recording a method for controlling a
Flying On Demand (FOD) voltage within a hard disk drive (HDD), the
HDD comprising a disk and a magnetic head that records data on or
reproduces data from the disk, and the method comprises; detecting
a shock applied to the HDD, and upon detecting the shock,
controlling the FOD voltage applied to the magnetic head to
thermally expand one end of the magnetic head.
[0011] In another embodiment, the invention provides a hard disk
drive (HDD) comprising; at least one disk, a magnetic head
recording data on the disk or reproducing data from the disk and
having one end that thermally expands in relation to an applied
Flying On Demand (FOD) voltage, a shock sensor detecting an
external shock applied to the HDD, and a controller controlling the
FOD voltage in response to a detected shock.
[0012] In another embodiment, the invention provides a hard disk
drive (HDD), comprising; at least one disk, a magnetic head
recording data on the disk or reproducing data from the disk and
having one end that thermally expands as a Flying On Demand (FOD)
voltage is applied, a shock sensor detecting an external shock
applied to the HDD, a controller generating a signal for removing
the FOD voltage when the shock sensor detects the shock, and a
pre-amplifier receiving the signal for removing the FOD voltage
from the controller and removing the FOD voltage applied to the
magnetic head.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The above and/or other aspects and advantages of the present
invention will become apparent and more readily appreciated from
the following detailed description, taken in conjunction with the
accompanying drawings of which:
[0014] Figure (FIG.) 1 is an exploded perspective view showing the
structure of a hard disk drive according to an embodiment of the
present invention;
[0015] FIG. 2 is a block diagram of a drive circuit of the hard
disk drive of FIG. 1; and
[0016] FIG. 3 is a flow chart for explaining the FOD voltage
control method of the hard disk drive of FIG. 1.
DESCRIPTION OF EMBODIMENTS
[0017] Reference will now be made to embodiments of the invention,
examples of which are illustrated in the accompanying drawings,
wherein like reference numerals refer to the like elements
throughout. The embodiments are described below in order to explain
the present invention by referring to the figures.
[0018] FIG. 1 is an exploded perspective view showing the structure
of a hard disk drive according to an embodiment of the present
invention. FIG. 2 is a block diagram of a drive circuit of the hard
disk drive of FIG. 1.
[0019] Referring to FIGS. 1 and 2, a hard disk drive (HDD) 100
according to an embodiment of the invention includes at least one
disk 110 for recording data, a spindle motor (SPM) 120 for rotating
the disk 110, a head stack assembly (HSA) 130 pivoting around a
pivot shaft 130a to move across the disk 110, a printed circuit
board assembly (PCBA) 140 for electrically controlling the HDD 100
and having a printed circuit board (PCB) on which most circuit
parts, in particular, a controller 170 which will be described
later, are installed, a base 150 on which the above constituent
parts are assembled, and a cover 160 covering the upper side of the
base 150 and forming a seal to protect the constituent parts from
outside dust and foreign materials.
[0020] One or more disks may be provided as the disk 110. When a
plurality of disks are provided as the disk 110, the plurality of
disks are separated a predetermined distance from one another to be
deposited above the base 150. Both sides of the disk 110 are coated
with a magnetic material of a thin film where data is stored. The
magnetic material is coated on a surface of the disk 110 in a
method such as electric plating, sputtering, chemical vapor
deposition, or physical vapor deposition.
[0021] The disk 110 typically includes a large number of tracks
formed of a plurality of concentric circles, actually several
hundred thousands of tracks. Each track has a plurality of data
sectors and each data sector can record a defined number of data
bytes (e.g., 512 Bytes). The data sector consists of a sector
header including the address information of a data sector, a data
section where data is actually recorded, and an error correction
code (ECC) to correct fine errors of the data.
[0022] As examples, the size of the disk 110 may be 1.0'', 1.8'',
2.5'', 3.5'', 5.25'', 8'', 14'', etc. The material forming the disk
110 may be an aluminum alloy, glass, a glass composition, and a
magnesium alloy, etc.
[0023] The spindle motor 120 is coupled to the disk 110 and rotates
the disk 110 in response to a control signal of a controller 170
which will be described later. The rotational angular speed of the
spindle motor 120 may be, for example, 3,600 rpm, 5,400 rpm, 7,200
rpm, and 10,000 rpm.
[0024] The HSA 130 pivots around a pivot shaft 130a to move a
magnetic head 131 to a desired position on the disk 110. The HSA
130 includes the magnetic head 131 recording or reproducing data
with respect to the disk 110, a slider 132 having the magnetic head
mounted thereof and allowing the magnetic head 131 to float above
the disk 110, a suspension 133 elastically supporting the slider
132 toward the surface of the disk 110, an actuator arm 134 coupled
to the pivot shaft 130a capable of pivoting and extending so that
the magnetic head 131 reaches the disk 110, and an actuator 135
rotating the actuator arm 134.
[0025] The magnetic head 131 can reproduce data from the disk 110
by detecting a magnetic field formed on the surface of the disk 110
or record data on the disk 110 by magnetizing the surface of the
disk 110. Although a single magnetic head is illustrated as the
magnetic head 131 in FIG. 2, the magnetic head 131 may be provided
as a recording head to magnetize the disk 110 and a reproducing
head to detect the magnetic field of the disk 110.
[0026] The magnetic head 131 may be arranged to float a
predetermined distance from each of both sides of the disk 110
stacked above the base 150. For example, when the number of the
disk 110 is six, twelve of the magnetic heads 131 may be arranged
to float above both sides of each of the disks 110.
[0027] The magnetic head 131 reproduces data from the disk 110 or
records data on the surface of the disk 110 in a state of floating
above the surface of the disk 110 as high as the flying height
(FH). When a high tracks per inch (TPI) and a high bits per inch
(BPI) are required in the manufacturing design of a high capacity
HDD, the width of each track decreases and accordingly the
intensity of a magnetic field is substantially weakened. Thus, for
the magnetic head 131 to smoothly detect the magnetic field, a
flying on demand (FOD) voltage is applied to the magnetic head 131
as a means for appropriately controlling the FH of the magnetic
head 131.
[0028] The magnetic head 131 is generally formed of a metal alloy
that is called as permalloy including Ni and Fe as main
ingredients. Thus, when an FOD voltage is applied to the magnetic
head 131 formed of permalloy metal alloy, a portion around a pole
tip of the magnetic head 131 protrudes due to a difference in
thermal expansion coefficients of metal components forming each
part of the magnetic head 131, which is called as thermal pole tip
protrusion (TPTP). Thus, the FH of the magnetic head 131 decreases.
In contrast, when the FOD voltage being applied to the magnetic
head 131 is decreased or removed, the pole tip of the magnetic head
131 that has protruded is thermally contracted and thus the FH of
the magnetic head 131 is decreased. The present invention adopts
and further develops this principle so that, as the controller 170
appropriately controls the FOD voltage applied to the magnetic head
131 as described later, the recording and reproduction ability of
the magnetic head 131 is improved while the collision between the
magnetic head 131 and the surface of the disk 110 is prevented. One
method of controlling the FOD voltage in this regard will be
described later.
[0029] The slider 132 physically supports the magnetic head 131 and
simultaneously makes the magnetic head 131 located at an accurate
position when the magnetic head 131 floats over the surface of the
disk 110. To provide such a function, the slider 132 preferably has
a streamlined shape such as a sled to use a lift force generated by
the rotation of the disk 110.
[0030] The suspension 133 connects the slider 132 and the actuator
arm 134 as described later and elastically supports the slider 132
toward the surface of the disk 110. Thus, the suspension 133
prevents the collision between the magnetic head 131 and the
surface of the disk 110 because the magnetic head 131 becomes too
close to the surface of the disk 110, or the deterioration of the
recording and reproduction ability of the magnetic head 131 because
the magnetic head 131 becomes too far from the surface of the disk
110, as the slider 132 moves in a large amplitude by a fine
vibration occurring to the HDD 100.
[0031] The actuator arm 134 has one end connected to the suspension
133 and the other end coupled to the pivot shaft 130a capable of
relatively rotating. The actuator arm 134 extends to a sufficient
length, such that the magnetic head 131 freely moves over the
surface of the disk 110.
[0032] The actuator 135 makes the actuator arm 134 rotate around
the pivot shaft 130a. The actuator 135 includes a voice coil (not
shown) and a magnet (not shown). The actuator 135 makes the
actuator arm 134 pivot in a direction following the Fleming's left
hand rule under the influence of an electromagnetic force generated
due to the interaction between a magnetic force generated by the
magnet and current flowing in the voice coil. The controller 170
controls the electromagnetic force to move the magnetic head 131 in
a desired direction on the disk 110.
[0033] Although the actuator 135 is shown as a voice coil motor
(VCM) in FIG. 2, the scope of the present invention is not limited
thereto and the actuator 135 may be, for example, a stepper motor
which rotates by a predetermined angle according to an input
signal. However, when the actuator 135 is the VCM, the VCM has the
advantages of resisting thermal effects, not needing periodic
formatting, and superior reliability.
[0034] The controller 170 controls the mechanical and electrical
operations of the HDD 100. It may be implemented using a
conventional digital signal processor (DSP), a microprocessor, and
a microcontroller, a recording medium recording software, and/or
firmware executing the method for controlling an FOD voltage, as
will be described later.
[0035] The controller 170, as shown in FIG. 2, controls (decreases
or increases) the rotational angular speed of the spindle motor 120
by inputting a control signal to the spindle motor 120, controls
the VCM 135 to move the magnetic head 131 to a designated data
sector, controls the magnetic head 131 to reproduce data from the
disk 110 or record data on the disk 110, and controls the FOD
voltage applied to the magnetic head 131 to improve the recording
and reproduction ability of the magnetic head 131 and
simultaneously prevent the collision between the magnetic head 131
and the surface of the disk 110. The controller will be described
in some additional detail with a drive circuit of the HDD 100
according to an embodiment of the present invention.
[0036] As shown in FIG. 2, the HDD 100 according to an embodiment
of the invention includes a pre-amplifier 171, a read/write channel
172, a host interface 173, a shock sensor 174, a VCM driver 136, a
spindle motor (SPM) driver 122, and the controller 170 controlling
the above elements.
[0037] The pre-amplifier 171 amplifies a data signal that the
magnetic head 131 reproduced from the disk 110, or recording
current converted by the read/write channel 172, and records the
amplified signal and current on the disk 110 through the magnetic
head 131. Also, the pre-amplifier 171 adjusts the FOD voltage
applied to the magnetic head 131 by receiving the control signal of
the controller 170.
[0038] The read/write (R/W) channel 172 converts the signal
amplified by the pre-amplifier 171 to a digital signal and
transmits the converted signal to a host device (not shown) through
the host interface 173, or converts data input by a user and
received through the host interface 173 to a binary data stream
that is easy to record and inputs the converted data to the
pre-amplifier 171.
[0039] The host interface 173 transmits the data converted to a
digital signal to the host device or receives the data input by the
user from the host device and inputs the data to the read/write
channel 172 through the controller 170. The shock sensor 174
detects a shock when the shock occurs to the HDD 100 and inputs a
signal indicating the occurrence of a shock to the controller
170.
[0040] The VCM driver 136 controls the amount of current applied to
the VCM 135 by receiving the control signal of the controller 170.
The SPM driver 122 controls the amount of current applied to the
spindle motor 120 by receiving the control signal of the controller
170.
[0041] The controller 170 included in the HDD 100 according to the
present embodiment controls the functions of reproducing data from
the disk 110 or recording data to the disk 110, controlling the VCM
135 to move the magnetic head 131 to a desired position on the disk
110, controlling the spindle motor 135 to control the rotational
speed of the disk 110, and controlling the FOD voltage applied to
the magnetic head 131 to thermally expand an end of the magnetic
head 131.
[0042] The functions of reproducing data from the disk 110 and
recording data to the disk 110 are respectively accomplished in a
data read mode and a data write mode. In the data read mode, a data
signal that the magnetic head 131 reads from the disk 110 is
amplified by the pre-amplifier 171, converted to a digital signal
by the read/write channel 172, and transmitted to the host
interface 172 through the controller 170 to be output to the host
device.
[0043] In the write mode, the user input data input from the host
device and received by the host interface 173 is input to the
read/write channel 172 through the controller 170, converted to the
binary data stream that is easy to record, amplified to recording
current by the pre-amplifier 171, and recorded on the disk 110 by
the magnetic head 131.
[0044] The function of controlling the VCM 135 to move the magnetic
head to a desired position on the disk 110 is implemented by the
controller 170, the VCM driver 136 adjusting the amount of current
applied to the VCM by receiving the control signal of the
controller 170, and the VCM 135 driven by the VCM driver 136. The
VCM driver 136 in response to the control signal of the controller
170 adjusts the amount of the current applied to the voice coil to
adjust the rotational force generated by the interaction between
the current flowing in the voice coil and the magnetic force of the
magnet. The rotational force of the VCM 135 drives the actuator arm
134 to pivot so that the magnetic head 131 is moved to a desired
position on the disk 110.
[0045] The function of controlling the spindle motor 120 to adjust
the rotational speed of the disk 110 is embodied by the controller
170, the SPM driver 122 adjusting the amount of current applied to
the spindle motor 120 by receiving the control signal of the
controller 170, and the spindle motor 120 driven by the SPM driver
122. The SPM driver 122 in response to the control signal of the
controller 170 adjusts the rotational speed of the spindle motor
120 by adjusting the amount of current applied to the spindle motor
120. Thus, the rotational speed of the disk 110 connected to the
spindle motor 120 is adjusted.
[0046] The function of controlling the FOD voltage which is applied
to the magnetic head 131 to thermally expand one end of the
magnetic head 131 is embodied by the shock sensor 174 detecting a
shock occurring to the HDD 100, the controller 170 receiving a
shock detecting signal from the shock sensor 174 and transmitting
an FOD voltage control command signal to the pre-amplifier 171, and
the pre-amplifier adjusting the FOD voltage applied to the magnetic
head 131 according to the command signal of the controller 170.
However, although the pre-amplifier 171 and the controller 170 are
connected directly and the pre-amplifier 171 directly receiving the
control signal from the controller 170 adjusts the FOD voltage
applied to the magnetic head 131 in FIG. 2, it is possible that the
pre-amplifier 171 and the controller 170 are indirectly connected
via the read/write channel 172 so that the pre-amplifier 171
indirectly receives the control signal of the controller 170
through the read/write channel 172 and adjusts the FOD voltage
applied to the magnetic head 131.
[0047] A method of controlling the FOD voltage applied to the
magnetic head 131 may be implemented by software executable by the
controller 170 in conjunction with other software resources (e.g.,
an operating system) and/or related firmware.
[0048] FIG. 3 is a flow chart for illustrating an exemplary FOD
voltage control method applicable to an embodiment of the
invention, such as the HDD of FIG. 1. As shown in FIG. 3, a method
for controlling an FOD voltage of an HDD according to an embodiment
of the present invention includes detecting a shock occurring to
the HDD 100 where the magnetic head 131 is mounted (S210) and
controlling the FOD voltage applied to the magnetic head 131 when
the shock is detected (S220).
[0049] In the operation of detecting a shock (S210), a shock
occurring to the HDD 100 is detected using the shock sensor 174
that is generally used. The shock occurring to the HDD 100 is not
limited to a strong stimulus caused by a collision as defined by a
dictionary, but has a wide meaning, for example, vibrations and
shakiness inevitably generated in an environment in which the HDD
100 is used.
[0050] In this case, considering the purpose of the present
invention to prevent the collision between the magnetic head 131
and the surface of the disk 110, it is preferred to install the
shock sensor 174 close to the magnetic head 131 or the surface of
the disk 110. However, since the recording and reproduction
performance of the magnetic head 131 may be affected by the shock
sensor 174, it is more preferred that the shock sensor 174 be
installed on the PCB.
[0051] In the operation of controlling the FOD voltage (S220), when
the shock sensor 174 detects a shock, by reducing or removing the
FOD voltage applied to the magnetic head 131, the pole tip of the
magnetic head 131 that has thermally expanded is thermally
contracted. Accordingly, the FH of the magnetic head 131 is
increased so that the possibility of the collision between the
magnetic head 131 and the surface of the disk 110 is reduced.
[0052] The operation of controlling the FOD voltage (S220) includes
storing a value of the FOD voltage applied to the magnetic head 131
(S240), reducing or removing the FOD voltage applied to the
magnetic head 131 (S250), and reapplying an FOD voltage
corresponding to the stored voltage value after the shock ends (or
ends) (S270). That is, by storing in advance the value of the FOD
voltage that is applied to the magnetic head 131 when the shock
occurs, after the shock ends, the operational state of the magnetic
head 131 is restored to the state before the shock occurs. Thus,
since the original state is restored within a short time after the
shock ends, the performance of the HDD 100 is improved. The phrase
"shock ends" recognizes that the application of an external
mechanical shock to an HDD is a highly transient event having a
finite period of incidence. The end or ending of a shock period may
be variously determined within embodiments of the invention.
[0053] The operation of reducing or removing the FOD voltage
applied to the magnetic head 131 (S250) includes distinguishing
whether the FOD voltage is applied to the magnetic head 131 (S251),
if the FOD voltage is not applied to the magnetic head 131 (NO),
maintaining the state in which the FOD voltage is not applied until
the shock ends and waiting for the disappearance of the shock
(S253), if the FOD voltage is applied to the magnetic head 131
(YES), controlling the FOD voltage applied to the magnetic head 131
(S252) and waiting for the disappearance of the shock (S253). That
is, the states of the FOD voltage not being applied to the magnetic
head 131 (NO) and being applied to the magnetic head 131 (YES) are
checked and, when the FOD voltage is not applied (NO), the
disappearance of the shock is waited for in a state that the FOD
voltage is not continuously applied (S253). When the FOD voltage is
applied (YES), after the FOD voltage is controlled (S252) and the
disappearance of the shock is waited for (S253). In this case, the
control of the FOD voltage (S252) substantially signifies reducing
or completely removing of the FOD voltage.
[0054] Preferably, the method further includes the operations of
stopping the operation of the magnetic head 131 when a shock is
detected (S230), before the operation of storing the value of the
FOD voltage applied to the magnetic head 131 (S240), and retrying
the operation of the magnetic head 131 after the shock ends (S260),
before the operation of re-applying the FOD voltage corresponding
to the stored voltage value to the magnetic head 131 (S270). That
is, when the shock sensor 174 detects a shock, to prevent the
collision between the magnetic head 131 and the surface of the disk
110 by increasing the FH of the magnetic head 131 with respect to
the disk 110, the operation of the magnetic head 131 is primarily
stopped (S230), the value of the FOD voltage applied to the
magnetic head 131 is stored (S240), the FOD voltage is reduced or
removed (S250), the operation of the magnetic head 131 is retried
after the shock ends (S26), and the FOD voltage corresponding to
the stored voltage value is reapplied to the magnetic head 131
(S270). Thus, any damage to the magnetic head 131 and/or the
surface of the disk 110 caused by the collision between the
magnetic head 131 and the surface of the disk 110 can be prevented
in advance. In this case, the operation of the magnetic head 131
may be a data read operation and/or a data write operation.
[0055] In the operational principle of the FOD voltage controlling
method according to the present embodiment, when the magnetic head
131 performs the reproduction of data recorded on the disk 110 (or
the recording of data on the disk 110), when a shock occurs to the
HDD 100, the shock sensor 174 arranged on the PCB of the HDD 110
detects the shock (S210).
[0056] The shock sensor 174 detecting the shock transmits a shock
detection signal to the controller 170. The controller 170
transmits a command signal to reduce or remove the FOD voltage to
the pre-amplifier 171. In this case, as mentioned above, the
controller 170 can directly reduce or remove the FOD voltage
without using the pre-amplifier 171.
[0057] The controller 170 stops the data reproduction operation of
the magnetic head 131 (S230). The value of the FOD voltage applied
to the magnetic head 131 is stored (S240). Whether the FOD voltage
is applied to the magnetic head 131, that is, the value of the FOD
voltage is "0", is distinguished (S251). When the FOD voltage is
applied to the magnetic head 131 (YES), the pole tip of the
magnetic head 131 thermally expands so that the distance between
the magnetic head 131 and the surface of the disk 110 decreases,
that is, the FH of the magnetic head 131 decreases. Thus, when a
shock occurs to the HDD 100, the magnetic head 131 and the surface
of the disk 110 are highly likely to collide with each other.
[0058] Thus, when the FOD voltage is applied to the magnetic head
131, that is, the value of the FOD voltage is not "0", the FOD
voltage applied to the magnetic head 131 is reduced or removed
(S252) and the pole tip of the magnetic head 131 is thermally
contracted. Accordingly, the distance between the magnetic head 131
and the surface of the disk 110 increases and the disappearance of
the shock is waited for (S253).
[0059] When the FOD voltage is not applied to the magnetic head 131
(NO), the distance between the magnetic head 131 and the surface of
the disk 110 is relatively great, that is, the FH of the magnetic
head 131 increases. Thus, even when a shock occurs to the HDD 100,
the possibility of the collision between the magnetic head 131 and
the surface of the disk 110 becomes low.
[0060] Consequently, when the FOD voltage is not applied to the
magnetic head 131, that is, the value of the FOD voltage is "0",
the current state in which the FOD voltage is not applied to the
magnetic head 131 is maintained until the shock ends and the
disappearance of the shock is waited for (S253).
[0061] After the shock ends, the controller 170 retries the data
reproduction operation of the magnetic head 131 (S260) and applies
the FOD voltage corresponding to the stored voltage value to the
magnetic head 131 (S270). Of course, when the FOD voltage has not
been applied to the magnetic head 131 (NO), since the value of the
FOD voltage has been "0", the value of the FOD voltage reapplied to
the magnetic head 131 is "0".
[0062] According to the method for controlling an FOD voltage of a
hard disk drive according to an embodiment of the present invention
(S200), since the FOD voltage is applied to the magnetic head 131
to lower the FH of the magnetic head 131, the recording and
reproduction ability of the magnetic head 131 are improved. Also,
when a shock occurs to the HDD 100, since the FH of the magnetic
head 131 is increased by reducing or removing the FOD voltage, the
possibility of the collision between the magnetic head 131 and the
surface of the disk 110 can be reduced.
[0063] In the above-described embodiment, when a shock occurs to an
HDD, although the FOD voltage applied to the magnetic head 131 is
reduced or removed by the controller 170 that is embodied by
software (S200), the above operation can be embodied by hardware
using the input and output of electric signals. That is, as shown
in FIG. 2, when a shock occurs to the HDD 100, the shock sensor 174
detects the shock and transmits an electric signal indicating that
the shock is detected to the controller 170. The controller 170
stops the recording and/or reproduction operations of the magnetic
head 131 based on the input electric signal and simultaneously
transmits an input signal indicating that the FOD voltage be
removed in synchronism with the signal to the pre-amplifier 171.
Then, the pre-amplifier 171 receives the input signal and instantly
removes the FOD voltage applied to the magnetic head 131.
[0064] As described above, when the method is embodied only by
hardware using the input and output of electric signals, not based
on additional software, when a shock occurs to the HDD 100, a
response speed to remove the FOD voltage from the magnetic head 131
in response to the shock becomes faster. Thus, when a shock occurs
to the HDD 100, damage to the magnetic head 131 and/or the surface
of the disk 110 can be certainly prevented.
[0065] According to the above-described embodiments of the present
invention, the recording and reproduction capabilities associated
with an HDD magnetic head are improved by applying an FOD voltage
to the magnetic head. Also, potential damage to the magnetic head
and/or the surface of the disk can be prevented by detecting an
externally applied shock to the HDD and reducing or removing the
FOD voltage in relation thereto.
[0066] Although several embodiments of the invention have been
shown and described above, the present invention is not limited to
only the described embodiments. Instead, it will be appreciated by
those skilled in the art that various changes may be made to these
embodiments without departing from the scope of the invention as
defined by the following claims and their equivalents.
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